1. Field of the Invention
The present invention relates to a high frequency switch or the like, of which main object is to switch a high frequency signal in a radio circuit of radio communication equipment such as a portable telephone.
2. Description of the Prior Art
High frequency switch circuits are often used to switch transmit/receive signals in radio circuits of radio communication equipment such as a portable telephone using TDMA systems.
Hereinafter, an example of conventional high frequency switch circuits described above will be described with reference to a drawing.
FIG. 13 shows an equivalent circuit diagram of an example of conventional high frequency switch circuits.
In FIG. 13, the anode of a first diode D1301 is coupled to a transmitting terminal 1301 through a first capacitor element C1301. Further, a control terminal 1302 is coupled to the anode side of the first diode D1301 through an inductor element L1301 and a resistor element R1301. Also, the anode of a second diode D1302 is coupled to a receiving terminal 1303 through a second capacitor element C1302, and the cathode of the second diode is connected to ground. Further, one end of a first transmission line TL1301, which has an electrical length of xc2xc wavelength at the operating frequency, is connected also to the anode side of the second diode D1302. The other end of the first transmission line is connected to the cathode of the first diode D1301, and also coupled to an antenna terminal 1304 through a third capacitor element C1303. Here, in order to decrease the variety of components to be used and thereby to reduce cost, usually, diodes having the same characteristics are used for the first diode D1301 and the second diode D1302.
The operation of the high frequency circuit configured as described above will be described.
In transmitting, when a positive voltage is applied to the control terminal 1302, the first diode D1301 and the second diode D1302 are turned on. At this time, the capacitor elements C1301, C1302, and C1303 block components of direct current. A transmit signal passes through the capacitor C1301 from the transmitting terminal 1301 and is transmitted to the antenna terminal 1304 through the first diode D1301 and the capacitor element C1303. Herein, the transmission line TL1301 operates as a xc2xc wavelength resonator having one end grounded, because the second diode D1302 is turned on. Therefore, the impedance of lines in the side of the antenna terminal 1304 becomes infinite and therefore no transmit signal is transmitted to the receiving side.
In receiving, no voltage is applied to the control terminal 1302, and therefore both the first diode D1301 and the second diode D1302 are in the OFF state. Thus, a receive signal is transmitted to the receiving terminal 1303 from the antenna terminal 1304 through the capacitor element C1303, the transmission line TL1301, and the capacitor element C1302.
PIN diodes are mainly used for the first diode D1301 and the second diode D1302, which are used for switching. However, generally, diodes have a tradeoff relationship that a diode of low ON resistance has a large capacitance between the cathode and anode terminals and a diode having a small inter-terminal capacitance in the OFF state has a high ON resistance.
Therefore, if importance is attached on isolation during receiving and therefore a diode having a small inter-terminal capacitance is selected to achieve high isolation, the signal path produces a large loss during transmitting because of the large ON resistance of the diode.
On the other hand, when importance is attached on insertion loss during transmitting and therefore a diode of a low ON resistance is selected, then there is a problem that the increased inter-terminal capacitance reduces isolation to result in a large loss produced by the signal path during receiving.
The present invention has been achieved in view of such problems, and has an object to provide a high frequency switch favorably reducing loss produced in signal paths both during transmitting and during receiving.
One aspect of the present invention is a high frequency switch, comprising:
a transmitting terminal;
a receiving terminal;
an antenna terminal;
a first diode having an anode electrically connected to said transmitting terminal and a cathode electrically connected to said antenna terminal;
a second diode having an anode connected through a transmission line of xc2xc wavelength to the antenna terminal which is electrically connected to said receiving terminal, and having the side of a cathode grounded; and
a control terminal provided to a node between said transmitting terminal and said first anode,
wherein said first and second diodes have a tradeoff relationship between ON resistance thereof and capacitance between said anode and said cathode, and
the ON resistance of the first diode is lower than the ON resistance of the second diode, and the capacitance of the second diode in the OFF state is smaller than the capacitance of the first diode in the OFF state.
Another aspect of the present invention is the high-frequency switch,
wherein a diode having a ON resistance of not higher than 1xcexa9 is used for said first diode and a diode having an inter-terminal capacitance of not larger than 0.8 pF in the OFF state is used for said second diode.
Still another aspect of the present invention is the high frequency switch,
wherein a diode having a ON resistance of not higher than 0.8xcexa9 is used for said first diode and a diode having an inter-terminal capacitance of not larger than 0.5 pF in the OFF state is for said second diode.
Yet still another aspect of the present invention is the high frequency switch,
Still yet another aspect of the present invention is the high frequency switch, further comprising a capacitor element or a parallel circuit of LC connected in series with said second diode.
A further aspect of the present invention is a high frequency switch, comprising:
a laminated component having a plurality of dielectrics laminated therein;
a transmitting terminal, a receiving terminal, an antenna terminal, a control terminal, a ground terminal, and an electrode pattern for connecting a part, which are provided on the surface of said laminated component;
a first diode having an anode electrically connected to said transmitting terminal and having a cathode electrically connected to said antenna terminal; and
a second diode having an anode connected through a transmission terminal of xc2xc wavelength to the antenna terminal which is electrically connected to said receiving terminal, and having the side of a cathode grounded, said first and second diodes being mounted on the surface of said laminated component,
wherein said first and second diodes have a tradeoff relationship between ON resistance thereof and capacitance between said anode and said cathode, and
the ON resistance of the first diode is lower than the ON resistance of the second diode, and the capacitance of the second diode in the OFF state is smaller than the capacitance of the first diode in the OFF state.
A still further aspect of the present invention is the high frequency switch,
wherein said high frequency switch is configured by using the laminated component.
A yet further aspect of the present invention is a two-band type of high frequency switch, comprising:
a second high frequency switch for use in a second frequency band higher than the first frequency band; and
a divider for sharing the same antenna between said first high frequency switch and said second high frequency switch by multiplexing and demultiplexing said first frequency band and second frequency band, the antenna terminal of said first high frequency switch and the antenna terminal of said second high frequency switch being electrically connected to each other,
wherein the high frequency switch is used for said first high frequency switch and said second high frequency switch.
A still yet further aspect of the present invention is the two-band type of high frequency switch,
wherein the ON resistance of said first diode of said second high frequency switch is made lower than the ON resistance of said first diode of said first high frequency switch, and
the capacitance of said second diode, in the OFF state, of said second high frequency switch is made smaller the capacitance of said second diode, in the OFF state, of said first high frequency switch.
An additional aspect of the present invention is the two-band type of high frequency switch,
wherein the ON resistance of said first diode of said first high frequency switch is not higher than 1xcexa9 and the ON resistance of said first diode of said second high frequency switch is not higher than 0.8xcexa9, and
the capacitance of said second diode, in the OFF state, of said first high frequency switch is not larger than 0.8 pF, and the capacitance of said second diode, in the OFF state, of said second high frequency switch is not larger than 0.5 pF.
A still additional aspect of the present invention is the two-band type of high frequency switch,
wherein a transmitting terminal, a receiving terminal, and a control terminal of said first high frequency switch, a transmitting terminal, a receiving terminal, and a control terminal of said second high frequency switch, and the antenna terminal common to said first high frequency switch and said second high frequency switch are provided on the surface of a laminated component having a plurality of dielectrics laminated therein, along with a ground terminal as electrode patterns for connecting parts, and said first high frequency switch, said second high frequency switch, and said divider are provided in the interior of said laminated component, and said first diode and said second diode are mounted on the surface of said laminated component.
A yet additional aspect of the present invention is a three-band type of high frequency switch, comprising:
a second high frequency switch for use in a second frequency band higher than the first frequency band;
a third high frequency switch for use in a third frequency band higher than the first frequency band;
a divider for sharing the same antenna among said first high frequency switch, said second high frequency switch, and said third high frequency switch, by multiplexing and demultiplexing said first frequency band, said second frequency band and said third frequency band, the antenna terminal of said first high frequency switch and the antenna terminal of said second high frequency switch being electrically connected to each other,
wherein the high frequency switch is used for said first high frequency switch and said second high frequency switch, and
said third high frequency switch has a third diode having a cathode connected to between said antenna terminal and a node of the cathode of said first diode and said transmission line and having an anode connected to a second receiving terminal, and a second control terminal connected to between said third diode and said second receiving terminal,
said third high frequency switch using the transmitting terminal of said first high frequency switch as a second transmitting terminal thereof, and said third high frequency switch operating on the receiving side, by using said second diode of said second high frequency switch.
A still yet additional aspect of the present invention is the three-band type of high frequency switch,
wherein the ON resistance of said first diode of said second high frequency switch and said third diode of said third high frequency switch are made lower than the ON resistance of said first diode of said first high frequency switch, and
the capacitance of said second diode, in the OFF state, of said second high frequency switch is made smaller than the capacitance of said second diode, in the OFF state, of said first high frequency switch.
A supplementary aspect of the present invention is the three-band type of high frequency switch,
wherein the ON resistance of said third diode of said third high frequency switch is lower than the ON resistance of said first diode of said second high frequency switch.
A still supplementary aspect of the present invention is the three-band type of high frequency switch,
wherein the ON resistance of said first diode of said first high frequency switch is not higher than 1xcexa9 and the ON resistance of said first diode of said second high frequency switch and said third diode of said third high frequency switch is not higher than 0.8xcexa9, and
the capacitance of said second diode, in the OFF state, of said first high frequency switch is not larger than 0.8 pF, and the capacitance of said second diode, in the OFF state, of said second high frequency switch is not larger than 0.5 pF.
A yet supplementary aspect of the present invention is the three-band type of high frequency switch,
wherein the ON resistance of said third diode of said third high frequency switch is made not higher than 0.5 xcexa9.
A still yet supplementary aspect of the present invention is the three-band type of high frequency switch,
wherein the transmitting terminal, receiving terminal, and control terminal of said first high frequency switch, the transmitting terminal, receiving terminal, and control terminal of said second high frequency switch, the receiving terminal and control terminal of said third high frequency switch, and the antenna terminal common to said first high frequency switch, said second high frequency switch, and said third high frequency switch are provided on the surface of a laminated component having a plurality of dielectrics laminated therein, along with a ground terminal as electrode patterns for connecting parts, and
electrode patterns for configuring said first high frequency switch, said second high frequency switch, said third high frequency switch, and said divider are provided in the interior of said laminated component, and said first diode, said second diode, and said third diode are mounted on the surface of said laminated component.
Another aspect of the present invention is radio communication equipment, comprising:
an antenna;
transmitting means for transmitting a signal from said antenna;
receiving means for receiving a signal from said antenna; and
switch means for switching the connection between said antenna and said transmitting means or said receiving means,
wherein the high frequency switch is used for said switch means.